# This code is part of Qiskit.
#
# (C) Copyright IBM 2021.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.

"""
RZX based template for CX - phase - CX
.. parsed-literal::
                                                                            »
q_0: ──■────────────────────────────────────────────■───────────────────────»
     ┌─┴─┐┌───────┐┌────┐┌───────┐┌────┐┌────────┐┌─┴─┐┌────────┐┌─────────┐»
q_1: ┤ X ├┤ RZ(ϴ) ├┤ √X ├┤ RZ(π) ├┤ √X ├┤ RZ(3π) ├┤ X ├┤ RZ(-ϴ) ├┤ RZ(π/2) ├»
     └───┘└───────┘└────┘└───────┘└────┘└────────┘└───┘└────────┘└─────────┘»
«                                    ┌──────────┐                      »
«q_0: ───────────────────────────────┤0         ├──────────────────────»
«     ┌─────────┐┌─────────┐┌───────┐│  RZX(-ϴ) │┌─────────┐┌─────────┐»
«q_1: ┤ RX(π/2) ├┤ RZ(π/2) ├┤ RX(ϴ) ├┤1         ├┤ RZ(π/2) ├┤ RX(π/2) ├»
«     └─────────┘└─────────┘└───────┘└──────────┘└─────────┘└─────────┘»
«
«q_0: ───────────
«     ┌─────────┐
«q_1: ┤ RZ(π/2) ├
«     └─────────┘
"""

import numpy as np
from qiskit.circuit import Parameter, QuantumCircuit


def rzx_zz1(theta: float = None):
    """Template for CX - RZGate - CX."""
    if theta is None:
        theta = Parameter('ϴ')

    qc = QuantumCircuit(2)
    qc.cx(0, 1)
    qc.rz(theta, 1)
    qc.sx(1)
    qc.rz(np.pi, 1)
    qc.sx(1)
    qc.rz(3 * np.pi, 1)
    qc.cx(0, 1)
    qc.rz(-1*theta, 1)

    # Hadamard
    qc.rz(np.pi / 2, 1)
    qc.rx(np.pi / 2, 1)
    qc.rz(np.pi / 2, 1)

    qc.rx(theta, 1)
    qc.rzx(-1*theta, 0, 1)
    # Hadamard
    qc.rz(np.pi / 2, 1)
    qc.rx(np.pi / 2, 1)
    qc.rz(np.pi / 2, 1)

    return qc
